Electrical selector switching apparatus



' Nov. 18, -1947. G. PETERSON ELECTRICAL SELECTOR swTTcHTNG APPARATUS 3 Sheets-Sheet 1 Filed Feb. 28, 194s INVENTOR. GLEN PETERSON Nov.` 18, 1947., G. PETERSON ELECTRICAL SELECTOR SWITCHING APPARATUS Filed Feb. 28, 1946 3 Sheets-Sheet 2 INVENTOR. GLEN PETERSON Nov. 18, 1947. G. PETERSON ELECTRICAL SELECTOR SWITCHING APPARATUS Filed Feb. 28, 1946 3 Sheets-Sheet 5 [N V EN TOR. GLEN PETERSON Patented Nov. 18, 1947 UNITED STATES ELECTRICAL SELECTOR SW/ETCHING APPARATUS (Granted under the act of March 3, 1833, as amended April 30, 1928; 37) 0. G. 757) 3 Claims.

lThe invention described herein may be manuiactured and used by or for the Government for governmental purposes, without the payment t me of any royalty thereon.

The present invention relates generally to automatic, selective switching mechanisms, and it is more particularly directed to such mechanisms as utilized in connection with radio apparatus, such as transmitters and receivers, to effect multifrequency changes therein.

rihe invention has reference to that type of selective switching mechanism which serves to connect one or more of a series of resonant networks, composed of inductive, capacitive, and resistive elements, to one or more electronic vacuum tubes, respectively, to effect tuning of the radio apparatus to a desired frequency or band of frequencies. The mechanism is responsive to a switch operation, as for example, by pressing a push button. Commonly in such mechanisms, a plurality of push buttons or control keys are employed, each corresponding to a particular frequency or band of frequencies, and means are employed for switching-in that resonant network which tunes the apparatus to the frequency or band of frequencies corresponding to the particular control key or button actuated.

Existing push button, selective switching mechanisms may be broadly divided into three general classes. There is one class wherein a switch is operated by direct mechanical coupling to the push button, said switch being an active part of and directly connected in the tuned resonant network. In the second class, oper-ation of a push button switch electrically actuates a second switch which may be a stepping type switch, said second switch being an active part of and connected directly in the tuned resonant network. The third class embraces those devices wherein the operation of the push button switch causes an electric motor to adjust the value of a single reactor, such as a variable condenser or variable inductor, to a selected position.

All of the above described switching mechanisins suiier from certain inherent limitations, principal of which are the following:

l. Long wire leads are often required between the switch, the lumped reactances which comprise the several tuned networks, and the electronic vacuum tubes which provide the required amplication or detection. These long leads limit the frequency range attainable, especially in the microwave region.

2. Only a very limited range of frequencies can be secured by those mechanisms in which the value of a single variable reactor is adjusted.

3. The switching mechanism is completely limited t0 service as a push button, single-station type, selector switch, and is not readily adapted to other uses in the same receiver, such as a bandchange switch.

4. The number of circuits which can be conveniently switched is limited to the number which can be arranged or mounted within the proximity of the push button.

With the continual expansion of the radio-frequency spectrum for communication purposes and with the extension of communication to higher frequencies, the above enumerated limitations of prior art, selective switching mechanisms make it increasingly diiiicult to encompass the enlarged radio spectrum in a single receiver. This is particularly true when amplitude-modulated broadcasting frequencies are assigned to a radio-frequency band that is widely separated from the band assigned to television broadcasting, which is, in turn, distantly spaced from the band assigned to frequency modulation.

Accordingly, it is the primary object of the present invention to obviate the limitations encountered in prior art, switching mechanisms, and to provide a new and improved automatic, selective switching mechanism capable of rapidly shifting the operating frequency of a radio apparatus over wide limits, involving ultra-high frequencies at one end ofthe spectrum and medium frequencies or low frequencies at the other end of the radio-frequency spectrum.

More specically, it is an object of this invention to provide an automatic, selective switching mechanism wherein the manually operated switch, such as a push button, is not an active electrical part of the radio-frequency circuit being switched.

Another object of this invention is to provide such a switching mechanism which will serve both as a single-station type of selector switch and as a band-change switch, either separately or in combination.

An additional object of this invention is to provide a switching mechanism of the above type which can be remotely controlled.

Still another object of this invention is to provide a switching mechanism of the above type, wherein the number of circuit elements or circuits being switchedpis not limited by the effectsy of capacitance, inductance, and stray coupling introduced by connecting leads fOr the Switch.

For a better understanding of this invention, as well as other objects and further features thereof, reference is had to the following detailed description to be read in connection with the accompanying drawings, wherein like components are designated by like numerals.

In the drawings:

Figure 1 is a schematic circuit of the radiofrequency stages of a superheterodyne receiver employed in conjunction with the invention;

Figure 2 is an elevational side viewof a, preferred embodiment of a selective switching mechanism, in accordance with the present invention;

Figure 3 is, an electrical diagram of the selective switching mechanism;

Figure 4 is a side elevation of the push button selector assembly included in the switching mechanism;

Figure 5 is a plan view of the movable contacts and contact ring of the push button selector assembly;

Figure 5 shows separately a single push button, and

Figure 7 is a plan view of the push button retaining and release discs of the push button selector assembly.

Referring now to Fig. 1, there is schematically shown the radio-frequency section of a conventional superheterodyne receiver, said section comprising a first radio-frequency amplifier stage, a second radio-frequency amplier stage, a local oscillator stage, and a mixer or converter stage. Vacuum tubes I0, II, I2, and I3` are incorporated in the respective stages. The operating frequency band of each stage is determined by a resonant network composed of various arrangements of inductors, capacitors, and resistors. Each stage is provided with a group of eight resonant networks, individual networks being tuned to distinct frequencies. The switching mechanism, in accordance with the present invention, is adapted to select a desired network from each group and insert the selected network in the associated stage.

The first network in the group of the first R.-F. stage is identified by numeral I4, and succeeding networks in this group are designated as IGI, MH, Hlm, IfiV, MV, etc. Succeeding networks of the other groups are identified in a like manner, the first `network in the second R.-F. stage group Ibeing identified by the numeral I5, the first network of the oscillator as I6, and the first network of the mixer as I'I. Since all the networks within a particular group are schematically alike, only `the r'st two networks of each group are shown herein. Each network is terminated in a set of four contact prongs, A, B, C, and D, and each stage is furnished with ay set of four stationary connector clips,v A', B', C', and D', adapted to engage said prongs. The clips AI, B1, C1, and DI in each stage, as is shown in the drawing, are wired to various auxiliary points, such as by-pass condensers, resistors, and vacuum tube terminals.

Each series of networks (a series consists of networks ill, i5, it, and I? or networks I4', I5', i5', and Ii', etc), when selected by the switching mechanism in response to the operation of a push button corresponding tothe selected series, serves to tune the radio-frequency section of the receiver to a particular frequency, this frequency being the median frequency of a band. To manually effect band tuning, variable capacitors i8, i 2G, and 2l are ypermanently included in the respective stages of the. circuit and are so connected whereby they shunt the inserted resonant network. The choice of networks within a group is preferably such as to enable coverage from the ultra-high frequency range to the medium frequency or long wave range, as desired.

It is to be understood that while in order to facilitate understanding, the invention is herein illustrated as employed in connection with four stages of a superhetcrodyne receiver, it is not limited either' to this number of stages nor to any specific circuit arrangement, but may be utilized in connection with any form of electrical apparatus wherein it is desired to selectively insert circuit elements.

Referring now to Fig. 2, one preferred embodiment of a switching mechanism is shown in a side elevational view, the mechanism being adapted to selectively switch the resonant networks in the circuit disclosed in Fig. 1. The switching mechanism is shown schematicaliy in Fig. 3. Y The mechanism comprises in the main a rotary turret receiver assembly 22 and a push button selector assembly 23 for controlling the angular position of the rotary turret. The eight networks in each group are all contained in shielded compartments (not shown) within a single cylinder, cylinder 24 being provided for the first R.F. stage, cylinder 25 for the second R.-F. stage, cylinder 26 for the oscillator stage, and cylinder 2 for the mixer stage. The Contact prongs A, B, C, and D, for each network, externally mounted at equi-spaced points across the cylinder and are insulated therefrom, the various sets of prongs being arranged along the circumference of the cylinder at equi-spaced positions. Cylinders 2t, 25, 26, and Ei'i are coaxially mounted in juxtaposition on a common shaft 28 whereby the network prongs in each series are in a linear arrangement. Cylinders to 2 combine to form a rotary turret which is axially rotated to a selected angular position by an electromagnetic actuator 2E! of any suitable design, preferably,T operating in a stepwise manner.

A framework is provided for the rotary turret structure 22 consisting of a base plate having standards 3l and EI' at opposite ends thereof. Shaft 28 is journalled at one extremity in a bearing attached to standard SI', the other extremity thereof being linked to electromagnetic actuator 29 which is affixed to standard 3I. Positioned Ibelow base plate 3) and parallel therewith is an insulation strip 32 having thefour setsr of connector clips A', B', C and D arranged longitudinally thereon, the clips in each set being so spaced as to engagea set of corresponding prongs A, B, C and D on the rotary turret when the prongs are brought into alignment therewith by actua-- tor 29.

interposed between cylinder 26 and actuator 29 is a rotary switch which comprises a brush assembly 33 having an insulation ring 35 perpendicularly supported below strip 32, with eight contact brushes IIE)v to II'I being arranged radially at equi-spaced points on the ring, and an indented metal disc 35 keyed to shaft 28 and ccoperating with brushes H0 to II'I.

Installed in suitable sockets mounted on base plate 3B of the framework are vacuum tubes iii to I3, and secured to the underside of plate 3B are the various components of Ythe circuit. The clips A', B', C' and D are wired to these tubes and components in accordance with the circuit diagram in Fig. 1.

Push button assembly 23 is provided with eight, circularly arranged push buttons 2i!) to E il Iwhich serve, when depressed, to electrically conn nect movable contacts 3l0 to 3H, respectively, to a common stationary ring contact 3b. Push button assembly Z3 is so designed whereby when an individual button is depressed any previously depressed button is released, hence only one push button switch is closed at any time. The mechanical operation of assembly 23 will become apparent in the consideration of Figs. e, 5, 6 and 7.

Electromagnetic actuator 29 is of any conventional design adapted to produce stepwise rotary motion, and is herein illustrated as comprising a held coil 3l which when energized causes an armature 38 to rotate. The rotation of armature 38 is periodically and momentarily arrested in the course of a full revolution by means of an interruptor switch 39, connected in series with eld 3l', the switch being actuated by the armature after a predetermined degree of movement is effected, so that armature 3! is caused to rotate in a stepwise manner. In this specic embodiment the operation of actuator 29 is such as to shift the turret until one series of prongs A, B, C and D engage stationary clips A B', C and D', at which point the turret dwells for a short interval and then continues its movement until the next series of prongs are brought into alignment, this movement continuing until those four prong sets associated with the series of networks selected by a push button corresponding thereto are in alignment with the clip sets, at which point the turret is brought to a complete stop. By dem pressing another push button, the turret again rotates until the prongs corresponding to this push button are in proper alignment.

The behavior of the device will be understood by examination of the schematic diagram. It will be seen that Contact ring :it is connected to indented disc 35 in series with the held 3l' of actuator 29 and a suitable power source represented by a battery dil. Movable contacts to Si? are directly wired to brushes Htl to ill', respectively, on the brush assembly 33. The armature 38 is mechanically coupled by shaft to both indented disc 35 and the rotary turret which includes cylinders 24 to 2l. Brushes il@ to lll are in physical and electrical contact with disc 35 as it rotates, with the sole exception of that brush whose position coincides with the indent formed on the disc.

To demonstrate the operation of the device, push button 2li! is shown in the depressed position, so that movable Contact 31! now establishes electrical Contact with ring 35. Assuming at the same time that the angular position of disc S5 is such that brush l it makes contact with disc Se at some point thereon, it will be seen that the electrical circuit from battery it to the field 3l of actuator 29 is completed through rotary switch 32 and the push button switch, thereby energizing the actuator and causing shaft 2t to rotate. This circuit is maintained until the angular position of disc S5 becomes such that indent coincides with brush liti, this being the condition shown in the schematic diagram, at which point the circuit is broken and the turret comes to a full stop. To select another series of networks, the corresponding push button is depressed, thereby releasing contact 3l@ from ring "i5 and causing the actuator 29 to rotate in a stepwise manner until the brush connected to the selected push button coincides with the indent on 6 disc 35, at which point the turret again comes to a full stop.

Referring now to Fig. 4, a preferred embodiment of a push button, selector switch assembly is shown including a supporting structure formed by a base plate 4|, an intermediate plate 42, and a top plate 43 arranged in axial succession and supported by spacer rod pairs iii and t5, the length of rods l5 being relatively short with respect to rods 44.

Eight push buttons 2l() to 2|'l are included in the assembly, only push buttons 2l il, ZlZ and 2 i4 being shown. The shape of an individual push button is shown separately in Fig. 6, the button having differently shaped sections identied by characters a to f. Tip a is a distinct member, being peg-shaped and of relatively small diameter with respect to the body of the button. Tip a is partially received in a central bore in the button, and is retained therein by means of a helical spring f which connects the tip d to the body of the button and tends to maintain the tip in its most extended position. The lower section b of the button is globular in shape, while section c is conically shaped, the maximum diameter of section c being somewhat greater than the maximum diameter of section b. Sections d and e are cylindrical, with the diameter of e being somewhat greater than d. Section e which Serves as the head of the button a convex upper surface to receive a nger tip.

Pivotally supported on its axis by a pedestal da, which is centrally mounted on base plate 43, are a pair of superposed saw tooth discs d1 and lili. These discs are shown separately in Fig. 7, where it will be seen that each disc is provided with eight saw teeth evenly spaced on the periphery thereof, the teeth of discs 4l" and 48 being arranged in opposition. Two arcuate slots are formed in disc el, and contained within the slots are helical springs 4S and the ends of the springs being connected to discs dl' and 4S in a manner whereby a torque is developed urging the opposing teeth of the two discs together.

Mounted directly on base plate @i and concentric With pedestal i5 is a stationary contact ring Sii. Circumferentially disposed about the contact ring at equi-spaced positions are eight wing-shaped movable contacts 35i! to Sii made of a resilient metal which are supported in a raised position above the contact ring so that normally one wing tip is superposed and disconnected-from the stationary contact ring 36. The contact ring 36 and movable contacts Sib to Si? are shown separately in plan view in Fig. 5.

When assembled, push buttons 2lb to 2H are inserted in apertures circularly arranged in discs l2 and 43, these apertures being aligned with the wing tips of movable contacts 3H] to 3H. The push buttons 2|() to 2H extend into the structure so that in its normal position the globularshaped section b of the push button is gripped between opposing teeth of discs 41 and 48, and the tip a of the push button is in close proximity to a movable contact. When a push button is depressed, the conical section d is forced between opposing teeth of discs 41 and 48. The push button is retained in the depressed position by saw tooth discs 41 and 48, the portions b and d defining a groove to receive the opposing teeth. In the depressed position the tip of the push button compels the associated movable contact to make connection with stationary contact ring 36, thereby closing the switch.

When a push button in a normal position is depressed, the conical surface d forces the opposing teeth of discs 4l and 48 to move suiliciently far apart so that a previously retained button is released. A helical spring 5l is provided for each push button which encircles portion d and is compressed between intermediate disc G2 and the shoulder formed by portion e. Thus when a push button is released, this spring restores the button to its normal position.

It is to be noted that since the leads running between the rotary turret structure 22 and the selector push button assembly 23 are not involved in the resonant circuits of the receiver, they may be extended to any desired length remote from the receiver without in any way affecting the receiver frequency,

While there has been shown what at present is considered a preferred embodiment of the invention, it is obvious that many changes and modications may be made therein without departing from the invention, and it is intended in the following claims to cover all such changes and mcdications as fall within the true spirit and scope of the invention.

What is claimed is:

i. A selective switching mechanism for tuning radio apparatus comprising a rotary turret, a plurality of resonant networks contained within said turret, each network having a distinct frequency characteristic and a like set of terminal prongs, the sets of said prongs being circumferential-ily arranged at equi-spaced external positions on said turret, a set of stationary connector clips adapted to engage a set of said prongs and associated with the radio apparatus to be tuned, a plurality of selector switches each corresponding to one of said plurality of networks, and means responsive to the operation ci a selector switch for rotating said turret to a position engaging the set of said prongs for the corresponding network with said set of clips.

2, A selective svitching mechanism for tuning radio apparatus comprising a rotary turret, a plurality of resonant networks contained within said turret, each network having a distinct frequency characteristic and a like set of terminal prongs, the sets of said prongs being circumferentially arranged at equi-spaced external positions on said turret, a set of stationary connector1 clips adapted to engage a set of said prongs and associated with the radio apparatus to be tuned, a plurality of selector switches each corresponding to one of said plurality of networks, an electromagnetic actuator coupled to said turret and operative in a stepwise manner whereby the sets of said prongs for each of said plurality of networks are sequentially engaged by said set of connector clips, and means responsive to the operation of any one of said selector switches for energizing said actuator for a period causing it to rotate said turret to the angular position whereby the set of said prongs for the corresponding network is engaged by said set of connector clips.

3. A selective switching mechanism for tuning radio apparatus comprising a rotary turret, a plurality of resonant networks contained within said turret, each network having a distinct frequency characteristic and a like set of terminal prongs, the sets of said prongs being circumferentially arranged at equi-spaced external positions on said turret, a set of stationary connector clips adapted to engage a set of said prongs and associated with the radio apparatus to be tuned, a plurality of two-terminal selector switches, one terminal being common, each of said selector switches corresponding to one of said plurality of networks, a, plurality of Xed brushes arranged circumierentially at radial positions corresponding to the sets of said prongs and connected to respective terminals of said plurality of selecto-r switches, a Contact disc having an indent and adapted to rotate with said turret in connection with said brushes excepting the brush coincident with the indent, an electromagnetic actuator including a field coil, said acuator being coupled to said turret and operative in a stepwise manner whereby a set of prongs from each of said plurality of networks is sequentially engaged by said set of connector clips, a source or power for said actuator, and means connecting said common terminal of said selector' switches to said contact disc in series with said source of power said held coil.

GLEN PETERSON.

CETED The following refe le of this patent:

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